Corrosion fatigue crack propagation of an aluminum alloy under periodic overloads

Periodic tensile overloads superposed on constant amplitude cycles were used on compact tension fracture mechanics specimens of an aluminum (Al–Cu–Mg) alloy. The delayed retardation of corrosion fatigue crack propagation in the low part of the Paris regime was investigated in a 3.5% NaCl environment. The aluminum alloy exhibits the intensive retardation effect of crack propagation under overload ratios from 1.3 to 2.0 and overload intervals from 10² to 10⁴ cycles. The crack propagation under the periodic overloads can be treated as the base constant amplitude crack propagation, i.e. . The periodic overloads decrease the crack propagation resistance coefficient of B_cf, but have less effect on the threshold value of obtained by best fitting of this model.